Following SVMP [1]}, the message \(\mathcal {M}_{f_{r_m}\rightarrow \beta } (\beta ) \)  from factor node \(f_{r_m}\)  to variable node \({\beta }\)  can be expressed as
\(\mathcal {M}_{f_{r_m}\rightarrow \beta } (\beta ) \propto \exp \left\lbrace  \left\langle {\log f_{r_m} ( {{r_m| h_m, \beta ^{-1}}} )} \right\rangle _{b\left( {h_m} \right) } \right\rbrace ,\\\) 
